a. Field of the Invention
The invention generally relates to oxidative treatment of non-aqueous phase liquids (NAPLs) and more particularly to the oxidative treatment of dense non-aqueous phase liquids (DNAPLs) using a single composition having a combination of at least one surfactant and at least one oxidant.
b. Background Art
Dependence on surface and ground water supplies for potable water has increased as the population of the world, and corresponding industrialization of the world, has increased. Increased industrial use of water supplies has resulted in decreased water quality throughout the world, due principally to industrial related release of pollutants into water supplies. One particularly important class of industrial pollutants is dense non-aqueous phase liquids, or DNAPLs.
Conventional DNAPL remediation is focused on pump- and treat methods which have proven relatively ineffective. The aqueous solubility of DNAPL compounds is typically a few thousand parts per million (ppm) or less, inherently making water-based contaminant flushing highly inefficient. (Mackay and Cherry, Environmental Science & Tech. 23, no. 630-636 (1989)). Recently, and within the past decade, surfactant-enhanced aquifer remediation (SEAR) and in situ chemical oxidation (ISCO) have shown promise for remediation of DNAPL subsurface contamination. Numerous field applications of SEAR indicate that significant efforts have been directed at aggressive DNAPL remediation using in situ flushing reagents (Palmer and Fish, USEPA, EPA/540/S-92/001, p 20; Abriola et al., Environmental Science & Tech., 27:2341-2351 (1993); Shiau et al., Ground Water, 32, no 4: 561-569 (1994); Sabatini et al., Ground Water, 35, no 6:954-963 (1997); Sabatini et al., Journal of Membrane Science, 151, no. 1:89-100 (1998); Sabatini et al., Journal of Contaminant Hydrology, 45:99-121 (2000)) as well as ISCO (Jerome, EPA/542/N97/004 (1997); Schnarr et al., Journal of Contaminant Hydrology, 29: 205-224) (1998); West et al., Oak Ridge National Lab, Oak Ridge, Tenn., p 101 ORNL/TM-13556 (1998); Lowe et al., EPA/625/R-99/012 US EPA ORG, Washington, D.C., 42-49 (2000); McKay et al., Chemical Oxidation and Reactive Barriers: Remediation of Chlorinated and Recalcitrant Compounds, Battelle Press, Columbus Ohio, p 009-116 (2000); Mott-Smith et al., Chemical Oxidation and Reactive Barriers: Remediation of Chlorinated and Recalcitrant Compounds, Battelle Press, Columbus Ohio, p 125-134 (2000)). No one method, i.e., pump and treat, ISCO or SEAR, has proven totally satisfactory with regard to DNAPL removal and all have limitations with respect to performance and cost. (U.S. EPA, 2003, The DNAPL Remediation Challenge: Is There a Case for Source Depletion?, EPA 68-C-02-092, Office of Research and Development, Washington D.C. (2003)).
U.S. Pat. No. 6,913,419 to Shiau describes methods for sequentially treating a subsurface DNAPL containing site with low concentrations of surfactant followed by an abiotic polishing process. This combination of treatments is an improvement over existing DNAPL treatment processes (pump and treat alone, SEAR alone or ISCO alone), but still requires a two step process that can be costly and time consuming.
Against this backdrop the present invention has been developed.